Production of tetrahydronaphthalene peroxide



P 18, 1951 R. JOHNSON PRODUCTION OF TETRAHYDRONAPHTHALENE PEROXIDE 2 Sheets-Sheet 1 Filed Nov. 2, 1948 FILTII PIES! A y f A sum:

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INVENTOR.

Pass 2 T JOHN-SON 09 7' TOE/Viz Patented Sept. 18, 1 951 PRODUCTION OF TETR-AHYDRO- NAPHTHALENE PEROXIDE Robert Johnson, Verona, Pa., assignor to Koppers Company, Inc., Pittsburgh, 'Pa., a corporation of Delaware Application November 2, 1948, Serial No. 57,967

3 Claims.

This invention relates to the production of tetrahydronophthalene peroxide. More particularly the invention relates to the production of tetrahydronaphthalene peroxide, alpha-tetralone and alpha-tetralol from tetrahydronaphthalene.

Tetrahydronaphthalene peroxide, a directoxidation product of tetrahydronaphthalene has been found to be an excellent ignition accelerator to increase the cetane number of fuels for high speed diesel engines. Alpha-tetralol and alphatetralone are products resulting from the oxidation of tetrahydronaphthalene which are good insecticides, good synthesis intermediates and,

very effective solvents for resins and plastics. These three products are produced by the process of the present invention.

In my application Serial No. 656,782 filed March 23, 1946, now U. S. Patent 2,462,103, I have de scribed a process of making tetrahydronap'hthalene peroxide from tetrahydronaphthalene (a compound readily available in commerce, such as the compound sold under the trade name, Tetralin) and a process for coverting the tetrahydronaphthalene peroxide to a mixture of alphatetralol and alpha-tetralone.

The primary object of the present invention is to provide a process by which the major portion of tetrahydronaphthalene is converted to tetrahydronaphthalene peroxide and a minor portion of tetrahydronaphthalene is recovered as alpha-tetralol and alpha-tetralone.

I have found that tetrahydronaphthalene peroxide may be separated from tetrahydronaphthalene and other reaction products formed in the oxidation reaction by precipitating the sodium salt of tetrahydronaphthalene peroxide and filtering to separate the salt from the mother liquor. The precipitation of the sodium salt of tetrahydronaphthalene peroxide is an important feature of the present invention because, if the sodium hydroxide solution is too dilute (less than 4% NaOH) the sodium salt will not precipitate but stay in solution. On the other hand if the sodium hydroxide solution is too concentrated (greater than NaOH), then a bulky gelatinous precipitate is formed which cannot be handled.

Another object of the invention is to provide a process by which tetrahydronaphthalene peroxide may be produced in such a form that it may be eifectively separated from the reaction products of the oxidation of tetrahydronaphthalene.

When tetrahydronaphthalene peroxide is converted into and precipitated as the sodium salt of tetrahydronaphthalene peroxide the mother liquor is made up of two solutions, i. e. an aqueous 2 NaOH solution and a hydrocarbon tetrahydronaphthalene solution. Each of these solutions has some tetrahydronaphthalene peroxide dissolved therein. The tetrahydronaphthalene with a minor portion of tetrahydronaphthalene peroxide may be recycled back to the oxidation converter for retreatment, but the aqueous sodium hydroxide solution contains both NaOH and sodium tetrahydronaphthalene peroxide which should be recovered to make the process economical. By heating the aqueous NaOH solution to a temperature of to C. the sodium tetrahydronaphthalene peroxide is converted into approximately equal parts of alpha-tetralone and alpha-tetralol along with some N aOH. Thus the solvents alpha-tetralol and alpha-tetralone are recovered and the NaOH solution is available for separating tetrahydronaphthalene peroxide from the oxidation reaction products.

Another object of the invention is to provide a process of producing tetrahydronaphthalene peroxide in which NaOI-I used for neutralizing the oxidation products and unconverted tetrahydro naphthalene are recovered and recycled back to the oxidation unit.

A further object of the invention is to provide a process of recovering alpha-tetralol and alphatetralone from the neutralizing solution used for separating tetrahydronaphthalene peroxide from the oxidation reaction products. 1

With these and other objects in view, the invention consists in the process of producing tetrahydronaphthalene peroxide as hereinafter described and particularly defined in the claims.

The various features of the invention are illustrated in the accompanying drawings in which Figures 1 and La show diagrammatically in flow sheet form an apparatus in which a preferred form of the invention may be carried out.

Referring to Figure 1, tetrahydronaphthalene is taken from a storage tank It) and pumped through a line l2 to a converter Id. In passing through the line H cupric carbonate, an oxidation catalyst, is introduced into the tetrahydronaphthalene through a line IS. The converter I4 is provided with a stirrer l8 and heating jacket 20 which act to agitate and maintain the oxidation reaction mass at a temperature of 80 to 0. Air from a line 22 is forced by means of a compressor 24 into the bottom of the converter [4 for the purpose of oxidizing the tetrahydronaphthalene. The tetrahydronaphthalene slowly added to the converter so that it remains in the converter for a period of two to five hours in which time the oxidation is completed to pro duce approximately 24% of tetrahydronaphtha- I lene peroxide.

The air and inert gases pass out of the converter through a condenser 26 wherein any oxidation products are condensed and returned to the converter.

The tetrahydronaphthalene peroxide together with unoxidized tetrahydronaphthalene and other oxidation products are forced through a line 28 by pump 38 to a cooler 32. In the cooler 32 the temperature is reduced to a temperature of to C. and the oxidation products are then discharged through a line 34 into a neutralizer 36.

The 'neutralizer is provided with a brine jacket 38 and a stirrer 40 by which the oxidation products are maintained at a .temperature of approximately 8 to 10 C. The oxidation products are neutralized by a sodium hydroxide solution which is drawn from a tank 42 and forced by pump 44 through a line 46 and hydrometer-controlled meter 48 into the neutralizer 36.

A 10% sodium hydroxide solution is normally maintained in the tank 42 and lvater is introduced into the line 46 through a line 50 through a control valve 52 in order to maintain approximately an 8 sodium hydroxide solution passing into the neutralizer. .As hereinafter described sodium hydroxide solution, as recovered by the process, is introduced into the line 46 through a line 54 to make up with sodium hydroxide from the tank 42 the 8% sodium hydroxide solution which flows into the neutralizer. In view of the fact that the sodium hydroxide being recycled in the process may vary in strength, it is necessary to maintain a hydrometer control with electric re.- lay 56 for control valve 52 in order to maintain a substantially 8% sodium hydroxide solution.

As hereinafter described the 8% strength sodium hydroxide solution is very important in order that the sodium tetrahydronaphthalene peroxide formed in the neutralizer, maybe precipitated as a granular material which may be readily filtered and easily washed. I

The precipitated sodium tetrahydronaphthalene peroxide, together with the reaction products, is forced through a line 58 by pump 60 into a filter press 62. The filtrate which is composed of sodium hydroxide solution, tetrahydronaph-' thalene, a small amount oftetralol and tetralone, together with tetrahydronaphthalene peroxide dissolved in the tetrahydronaphthalene, is passed through a line 64 to be treated as hereinafter I described.

After the filtrate is removed, the precipitate is washed by means of toluol which is held in a tank 66. The toluol is taken from the tank 66 through a line 68 by means of a pump II! to the filter press. The toluol washings from the filter press pass through a line I2 into a kettle 14 of a fraction-'- ating still 16. The distilled toluol passes overhead through a condenser 18 and then flows back to the tank 66'. In place of toluol other aromatic hydrocarbon solvents such as benzene and xylene, and also ether, may be used for washing the sodium tetrahydronaphthalene peroxide. Impurities including tetrahydronaphthalene are withdrawn from the still potthrough' a line I8 and this tetrahydronaphthalene is then returned to the line I2 through a, line (Figure 1). Some of the toluol will be lost in the washing operation and make-up toluene-may be added to the tank 66 through a line 82.

The precipitated sodium tetrahydronaphthalene peroxide dissolved in water is passed from the filter press 62 through a line 84 to a neutralizer 86. The sodium tetrahydronaphthalene peroxide is maintained in the filter press 62 and neutralizer 86 at a temperature of 8 to 10 C. to prevent the tetrahydronaphthalene peroxide from being broken up into tetralone and tetralol. To assist in maintaining this temperature a brine jacket 88 surrounds the neutralizer 86 and a stirrer actively agitates the sodium tetrahydronaphthalene product to bring it to a uniform temperature. The. neutralization of the sodium tetrahydronaphthalene peroxide is carried out by means of sulphuric acid which is taken from a tank sfl and pumped through a line 92 into the neutrali'zer. The sulphuric acid reacts with the sodium tetrahydronaphthalene peroxide to form sodium sulphate and set free tetrahydronaphthalene peroxide. The tetrahydronaphthalene peroxide is passed through a line 94 to a filter press 86 where it is filtered and washed with water. The water is taken from a tank 88 and pumped through a line' I66 to the filter press. The sodium sulphate exhausts from the filter press through lines I62 and the washed tetrahydronaphthalene peroxide in solid form is removed from the filter and transferred to a drier I66 as indicated by a line I04.

The tetrahydronaphthalene peroxide is preferably dried in a vacuum. To accomplish this the wet tetrahydronaphthalene peroxide is introduced into the drier I86 which is heated by hot water to a temperature below 50 C. and when sufiiciently dry, is conducted through a line I 88 to a closed container. III). A vacuum' pump H2 is connected through a condenser I I4 to the vacuum drier.

The filtrate removed from the filter press 62 is treated in a reactor H6 (Figure 1a) which is connected with the line 64. The reactor II 6 is provided with a heating jacket I I8 by which the temperature of the mixture of tetrahydronaphthalene, tetrahydronaphthalene peroxide, tetralol and tetralone are heated to a temperature of 80 to C. To make this heating effective a stirrer I20 is operated to provide a uniform temperature throughout. In the heating, the tetrahydronaphthalene peroxide is changed to a mixture of approximately 49% alpha-tetralol and 51% alpha-tetralone. To assist in recovering all of the tetrahydronaphthalene j dissolved in the caustic soda solution, additional caustic soda is taken from a tank I22 and pumped through a line I24 to increase the strength of the caustic in the reactor H6. The caustic solution having the tetralone and tetralol therein is passed from the reactor I I6 through a line I26 into asettling chamber I28. The caustic soda solution settles to the bottom of the chamber I28 and may be withdrawn through a line I30 to be discarded or preferably the caustic soda solution is sent through a line I32 back to the line 54 (Figure 1) to be used in the neutralizer 36 as hereinbefore referred to.

The supernatant solution in the settling chamber I28 is withdrawn through a line I34 and pumped into a receiver I36. This solution is composed of tetrahydronaphthalene, alpha-tetralone and alpha-tetralol. The solution passes from the tank I36 through a line I38 into the mid-portion of a fractionating still I40. The still pot is heated by coil I42 to drive overhead tetrahydronaphthalene which passes through condensers I44 into a receiver I46. The still I46 is preferably maintained under a vacuum by means of a vacuum pump I46which is connected with the receiver :0. By maintaining the temperature below 150 the. alphaetetralol is not decomposed. The tetrahydronaphthalene may be. withdrawn tromthe receiver by means of a pump I50 and passed through a line l? back to the line 80 (Figure 1') to .be again oxidized in the oxidizer l4. Thebottomsproduct of thestlll M0. is composed of tetrahydronaphthalene, alpha tetralone, alpha-tetralol and some neutralized products. This mixture is pumped from the still by means of pump i5 2. through a line I54 into a receiver I50. From the receiver the solution passes through a line ['58 into a still I60. The. impure tetralol and tetralone mixture is distilled in the still IEO under a vacuum of approximately 5.0 mm. of'mercury which is maintained by means. of a vacuum, pump I02 connected with the upper portion of a receiving tank [64. The purified mixture of alpha.- tetralol and alpha-tetralo'ne are conveyed through a line I66 to a storage. tank I68. The bottoms composed principally of impurities are pumped from the still I60 through a. line I into a storage tank I12.

In Table. I is shown'thedistribution of tetrahydronaphthalene peroxide in thesodium hydroxide or water layer and in the hydrocarbon or tetrahydronaphthalene layer when using dinerent strengths of sodium hydroxide. The oxidation was carried out ata temperature of 80 C. and the oxidation continued until approximately 24% of the tetrahydronaphthalene peroxide is formed from the tetrahydronaphthalene. With the 2% caustic it is very diflicult to separate the tetrahydronaphthalene peroxide from the reaction products, in fact a goodseparation of tetrahydronaphthalene peroxide from the reaction products cannot be obtained with a caustic soda solution less than 6%. In treatment with 8% caustic 84% of the peroxide originally present in the oxidized tetrahydronaphthalene is extracted from the tetrahydronaphthalene and 16% remains in solution in the tetrahydronaphthalene. The peroxide remaining in the tetrahydronaphthalene together with the sodium tetrahydronaphthalene peroxide present in the. aqueous caustic solution after filtration is recovered as explained above as a mixture of approximately equal parts of alpha-tetralol and alpha-tetralone.

TABLE I Extraction of tetrahydronaphthalene peroxide from tetrahydronaphthalene with aqueous alkaline solutions "Concentration of tetrahydronaphthalene peroxide in tetrahydronaphthalene 24%.]

Peroxide Content of Hydrocarbon and Aqueous Layers after Tempem' Extraction ture, Degrees 0.

Concentration of Alkali in Aqueous Solution Water Layer Hydrocarbon Layer tetrahydronaphthalene. peroxide with 6%. and 8% NaOH the measurements of tetrahydronaphthalene peroxide concentration in the. aqueous caustic layer were made. before crystallization began. The 6% and 8% caustic solutions are supersaturated solutions of the peroxide and upon standing crystals of sodium tetrahydronaphthalene peroxide will separate from the solutions.

In Table II is shown the solubility of tetrahydronaphthalene peroxide in sodium hydroxide solution. It may be stated that no crystals of sodium tetrahydronaphthalene peroxide are formed when neutralizing the oxidized products with a 4 caustic soda solution.

From the tables it will be seen also that the amount of tetrahydronaphthalene peroxide which remains in tetrahydronaphthalene decreases as the concentration of the caustic soda increases. On the other hand, the amount of tetrahydronaphthalene peroxide which is removed by the causticsoda solution increases as the concentration of the caustic soda increases. It has been found, however, that 8% concentration is quite critical in giving an effective recovery of the tetrahydronaphthalene peroxide and maintaining the tetrahydronaphthalene peroxide in a suitable crystalline form by which it may be readily filtered.

TABLE II Solubility of tetrahydronaphthalene peroxide in sodium hydroxide solutions The concentrations of tetrahydronaphthalene peroxide as shown in Table II are expressed in grams of tetrahydronaphthalene peroxide per 100 m1. of solution.

As an example of the present invention 25,750 lbs. of tetrahydronaphthalene per day was oxidized in the presence of 25.8 lbs. of cupric carbonate catalyst at 90 C. and 65 lbs. p. s. i. For the oxidation 221,800 cubic feet of air measured at 60 F. and atmospheric pressure were passed through the tetrahydronaphthalene. The reaction product was cooled to 10 C. and neutralized with 28,900 lbs. of 8% sodium hydroxide solution. The solution was then filtered to separate a sodium salt of tetrahydronaphthalene peroxide which was washed with 898 gallons of toluene and neutralized with 9,866 lbs. of 10% sulphuric acid solution. The neutralized precipitate was again filtered at 10 C. and washed with 6,186 lbs. of water and then dried in a vacuum at 30 to 40 C. to recover approximately 3,000 lbs. of tetrahydronaphthalene peroxide. The filtrate from the first filtration of the tetrahydronaphthalene peroxide was composed of 18,415 lbs. of tetrahydronaphthalene, 1026 lbs. of alpha-tetralol and alpha tetralone mixture with 1014 lbs. of tetrahydronaphthalene peroxide in an organic layer and 2163 lbs. of tetrahydronaphthalene peroxide in a water layer. This filtrate was treated with 5025 lbs. of 70% solution of sodium hydroxide and heated at a temperature of 60 to C. with active stirring. This heating reaction converts the aoeaese sodium salt of tetrahydonaphthalene peroxide to a mixture, of substantially equal parts of alphatetralol and alpha-tetralone, and'sodium hydroxide. The heated mixture is then decanted to separate an aqueous'layer and an organic layer.

The organic layer was then distilled'under obtaining a high yield of tetrahydronaphthaleneperoxide from said reaction mixture-Which oomprises forming a granular precipitate of the sodium compound of tetrahydronaphthalene peroxide by neutralizing said reaction mixture with adilute solution of caustic soda containing about 8 to 10 percent of sodium hydroxide While cooling said reaction mixture and caustic solution to a temperature below 15 C. to remove the heat of neutralization, filtering out said granular precipitate from supernatant liquid, recovering free tetrahydronaphthalene' peroxide from said precipitate by acidification, and drying the free tetrahydronaphthalene peroxide in a vacuum at a temperature below 50 C.

2. In the production of tetrahydronaphthalene peroxide wherein tetrahydronaphthalene is oxidized by oxygen-containing gas'to form a reaction mixture containing a substantial amount of tetrahydronaphthalene peroxide, the" method of obtaining a high yield of tetrahydronaphthalene peroxide from said reaction mixture which comprises forming a granular precipitate of the sodium compound of tetrahydronaphthalene peroxide by neutralizing said reaction mixture with a dilute solution of caustic solution containing substantially 8 percent of sodium hydroxide 'while maintaining said reaction mixture at-a temperature of about 10 C., filtering out said granular precipitate from supernatant liquid, recovering. free' tetrahydronaphthalene. peroxide from said precipitate by acidification at a temperatureof about 110 C., and drying the free tetrahydronaphthalene peroxide ina vacuum at a temperature below 50 C. v

3. In a process for the production of tetrahydronaphthalene peroxide wherein tetrahydronaphthalene is oxidized by. oxygen-containing gas in an oxidation zone to form a reaction mixture containing asubstantial amount of tetrahydronaphthalene peroxide, the "method ofobtaininga high recycle yield of tetrahydronaphthalene peroxidein said process which comprises forming 'a granular precipitate :of the sodium compound of tetrahydronaphthalene peroxide by neutralizing said reaction mixture with a dilute solution of caustic solution containing about 8 to 10 percent'of sodium hydroxide while maintaining said reaction mixture at a temperature of about 10 C'., filtering out said granular precipitate from supernatant liquid, recovering free tetrahydronaphthalene peroxide from'said precipitate by? acidification at a temperature of about 10 0., drying-the freetetrahydronaphthalene peroxide in a vacuum at a temperature below 50 0., recovering unreacted, tetrahydronaphthalene from the filtrate from the'separa tionof the sodium compound of tetrahydronaphthalene peroxide and recycling the tetrahydronaphthalene so recovered to'theoxidation zone.

ROBERT Jamison R FER C I DJJ; .The following reference's'fare ofllrecordrin the file oithis patent:

' uN rED'sT rEsrAT nTs I g Number v Name 4, I

1,924,786 j j Hartmann Aug. 29,1933 2,436,864 Johnson. Mar. 2; 1948 2,454,804 Johnson Nov, 30,1948 

1. IN THE PRODUCTION OF TETRAHYDRONAPHTHALENE PEROXIDE WHEREIN TETRAHYDRONAPHTHALENE IS OXIDIZED BY OXYGEN-CONTAINING GAS TO FORM A REACTION MIXTURE CONTAINING A SUBSTANTIAL AMOUNT OF TETRAHYDRONAPHTHALENE PEROXIDE, THE METHOD OF OBTAINING A HIGH YIELD OF TETRAHYDRONAPHTHALENE PEROXIDE FROM SAID REACTION MIXTURE WHICH COMPRISES FORMING A GRANULAR PRECIPITATE OF THE SODIUM COMPOUND OF TETRAHYDRONAPHTHALENE PEROXIDE BY NEUTRALIZING SAID REACTION MIXTURE WITH A DILUTE SOLUTION OF CAUSTIC SODA CONTAINING ABOUT 8 TO 10 PERCENT OF SODIUM HYDROXIDE WHILE COOLING SAID REACTION MIXTURE AND CAUSTIC SOLUTION TO A TEMPERATURE BELOW 15* C. TO REMOVE THE HEAT OF NEUTRALIZATION, FILTERING OUT SAID GRANULAR PRECIPITATE FROM SUPERNATANT LIQUID, RECOVERING FREE TEATRAHYDRONAPHTHALENE PEROXIDE FROM SAID PRECIPITATE BY ACIDIFICATION, AND DRYING THE FREE 